HOKX EXPEDITION — PAL/EONTOLOGY. 99 



Orthoceras ibiciforme, sp. nov. (Plate I., Figs, la, Id.) 



S/. char. — Shell elongate, straight, rate of increase one in seven ; section 

 rouncUy oblong ; surface ornamented with rounded annulations having an obliquity 

 of aljout 8". The distance from one annulation to another is one-third the maj(jr 

 diameter (in the single example with a test \w secondary ornamentation is visible, 

 but as the exterior is somewhat weathered, the presence or absence of sculpture is 

 uncertain). Septa 1'5 mm. apart, where the shell has a major diameter of 15 mm. 

 Si})liuncle lateral, liut cannot be further described, as in the only specimen contain- 

 ing septa the twu septa only visible are broken down around the siphunclo. 

 Body-chamber unknown. 



Obs. — This species lesemljles O. iluw, 8owerl)y, but the annulations are wider 

 apart, as four to three. The cnjss-section of O. ibex seems not to be definitely 

 ascertained, as IJlake " Brit. Foss. Ceph," p. 95, says, "it may therefore be naturally 

 elliptical ; " whilst Foord " Cat. Foss. Ceph., Brit. INIus.," i., p. 51, on the other hand 

 writes " section circular;" in which latter case the Larapintine fossil is further 

 distinguished by its elliptical section. Ortlwceras, sp. ind., t. -i, f. 5 in Johnston's 

 Cieol. Tasmania, may possibly belong here. 



Loc. — In limestone. Middle Valley at Teinpe Downs, Petermann Creek. 



Oi^thocepas microlineatum, sp. nov. (Plate II., Figs. \<da, \^b.) 



Sp. char. — Shell elongate, straight, rate of increase one in six ; sc^ction 

 almost circular. Suiface ornamented with slightly elevated, oblique and bisinuate 

 annulations (seven in a length of 17 nnn.); sculptured all over with wavy 

 threadlets (invisible to the unaided eye), separated by incised lines (about forty in 

 a width of 5 mm.), which are coincident with the annulations. Siphuncle marginal, 

 lai-ge, nearly one-third the diameter of the shell. Septa and body-chamber 

 uidxuown. 



Obs. — This Larapintine fossil is much like O. dtiponti, Barraiide, having the 

 same general character of primary and secondary ornament, the excentric 

 siphuncle, and circular .section of that .species ; but the annulations are wider 

 apart, as fourteen to eight, and the microscopic ornament is \ery much iiiier antl 

 densely ciowded. Externally it is distinguishable from O. ibicijonuc l)y its 

 circular section and more approximate annulations ; in O. ibiciforme there are four 

 (nearly) rings in a length of 17 nnn., whilst there are seven in O. inicrolinealuin in 

 the same length of shell of equal size. 



